Stabilized compositions

ABSTRACT

Improved processabiity and thermal stability is demonstrated by stabilized compositions comprising a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon having incorporated therein a stabilizing quantity of a stable organic free radical.

FIELD OF THE INVENTION

This invention relates to certain stabilized compositions comprising alinear alternating polymer of carbon monoxide and at least oneethylenically unsaturated hydrocarbon. More particularly, it relates tosuch polymer compositions of improved processability and heat stability.Background of the Invention

The class of polymers of carbon monoxide and olefin(s) has been knownfor some time. Brubaker, U.S. Pat. No. 2,495,286, produced such polymersof relatively low carbon monoxide content in the presence of freeradical initiators, e.g., peroxy compounds. U.K. No. 1,018,304 producedsimilar polymers of higher carbon monoxide content in the presence ofalkyl-phosphine complexes of palladium as catalyst. Nozaki extended thereaction to produce linear alternating polymers in the presence ofaryl-phosphine complexes of palladium moieties as catalyst and certaininert solvents. See, for example, U.S. Pat. No. 3,694,412.

More recently, the class of linear alternating polymers of carbonmonoxide and at least one ethylenically unsaturated hydrocarbon hasbecome of greater interest in part because of the greater availabilityof the polymers. The more recent processes for the production of thesepolymers, now becoming known as polyketones or polyketone polymers, areillustrated by a number of published European Patent Application Nos.including 121,965, 181,014, 213,671 and 257,663. The process, nowbroadly conventional, typically involves the use of a catalystcomposition formed from a compound of a Group VIII metal selected frompalladium, cobalt or nickel, the anion of a non-hydrohalogenic acidhaving a pKa below about 6, preferably below 2, and a bidentate ligandof phosphorus, arsenic or antimony.

The resulting polyketone polymers are relatively high molecular weightmaterials having established utility as premium thermoplastics in theproduction of shaped articles by methods conventional for the processingof thermoplastics. Although the polymers are relatively stable, thepolymers do undergo some loss of desirable properties when exposed toelevated temperatures or when subjected to repeating cycles of meltingand solidification.

Russell et. al, U.S. Pat. Nos. 3,929,727 and 4,024,104, teach the use ofcertain hindered phenolic benzophenones and benzotriazoles as thermalstabilizers of certain polymers of carbon monoxide and ethylene with theoptional presence of third monomers. Although the scope of thedisclosure of polymers by Russell et al is rather broad and includeslinear alternating polymers, the scope of the materials tested is rathernarrow and the Russell et al teachings do not appear to be directedtoward linear alternating polymers. It would be of advantage to provideadditional materials which will impart melt stability and heat stabilityto linear alternating polymers of carbon monoxide and at least oneethylenically unsaturated hydrocarbon.

SUMMARY OF THE INVENTION

The invention provides polymer compositions stabilized against theadverse effect of exposure to elevated temperature which are furthercharacterized by improved processability. More particularly, theinvention provides compositions comprising linear alternating polymer ofcarbon monoxide and at least one ethylenically unsaturated hydrocarbon,which compositions demonstrate improved thermal stability and meltstability upon incorporation within the linear alternating polymer ofcertain hindered phenolic stabilized free radicals.

DESCRIPTION OF THE INVENTION

The composition of the invention comprise linear alternating polymer ofcarbon monoxide and at least one ethylenically unsaturated hydrocarbonstabilized by the incorporation within the polymer of certain hinderedphenolic stabilized free radicals. The ethylenically unsaturatedhydrocarbons useful as the precursors of the linear alternating polymershave up to 20 carbon atoms inclusive, preferably up to 10 carbon atomsinclusive, and are aliphatic such as ethylene and other α-olefinsincluding propylene, 1-butene, isobutylene, 1-hexene, 1-octene and1-dodecene, or are arylaliphatic having an aryl substituent on anotherwise aliphatic molecule, preferably an aryl substituent on a carbonatom of the ethylenic unsaturation. Illustrative of this latter class ofethylenically unsaturated hydrocarbon are styrene, p-methylstyrene,p-ethylstyrene and m-isopropylstyrene. Preferred polyketone polymers arecopolymers of carbon monoxide and ethylene or terpolymers of carbonmonoxide, ethylene and a second hydrocarbon of at least 3 carbon atoms,particularly an α-olefin such as propylene.

The structure of the polyketone polymers is that of a linear alternatingpolymer and the polymer contains substantially one molecule of carbonmonoxide for each molecule of unsaturated hydrocarbon. When thepreferred terpolymers are to be stabilized according to the inventionthere will be within the polymeric chain at least about two unitsincorporating a moiety of ethylene for each unit incorporating a moietyof the second hydrocarbon. Preferably there will be from about 10 unitsto about 100 units incorporating a moiety of ethylene for each unitincorporating a moiety of the second hydrocarbon. The polymer chain ofthe preferred polymers is therefore represented by the repeating formula

    --CO--CH.sub.2 --CH.sub.2)].sub.x [CO--G)].sub.y           (I)

wherein G is a moiety of the second hydrocarbon of at least 3 carbonatoms polymerized through the ethylenic unsaturation. The --CO--CH₂ CH₂-- units and any --CO--G-- units are found randomly throughout thepolymer chain and the ratio of y:x is no more than about 0.5. In themodification of the invention employing copolymers without the presenceof a second hydrocarbon, the polymer is represented by the above formula(I) wherein y is zero. When y is other than zero, i.e., terepolymers areemployed, the preferred ratios of y:x are from about 0.01 to about 0.1.The end groups or "caps" of the polymer chain will depend upon whatmaterials were present during the production of the polymer and how orwhether the polymer has been purified. The precise nature of the endgroups does not appear, however, to be of any particular significance sofar as the overall properties of the polymer are concerned so that thepolymer is fairly represented by the formula for the polymer chain asdepicted above.

Of particular interest are the polyketone polymers of number averagemolecular weight from about 1000 to about 20,000, particularly thosepolymers of number average molecular weight from about 20,000 to about90,000 as determined by gel permeation chromatography. The physicalproperties of the polymers will depend in part on the molecular weight,whether the polymer is a copolymer or a terpolymer and, in the case ofterpolymers, the nature of and the proportion of the second hydrocarbonpresent. Typical melting points for the polymers are from about 175° C.to about 300° C. but preferred polymers have melting points from about210° C. to about 275° C. The polymers have a limiting viscosity number(LVN), measured in m-cresol at 60° C., of from about 0.4 dl/g to about10 dl/g but more often from about 0.8 dl/g to about 4 dl/g.

The process for the production of the polyketone polymers is illustratedby the above published European Patent Applications and a process nowbecoming broadly conventional is to contact the carbon monoxide andethylenically unsaturated hydrocarbon in the presence of a catalystcomposition formed from a palladium compound, the anion of anon-hydrohalogenic acid having a pKa (measured in water at 18° C.) ofbelow about 6, preferably below 2, and a bidentate ligand of phosphorus.The scope of the process for polymerization is extensive but, withoutwishing to be limited, a preferred palladium compound is a palladiumalkanoate, particularly palladium acetate, a preferred anion is theanion of trifluoroacetic acid or p-toluenesulfonic acid and a preferredbidentate phosphorus ligand is 1,3-bis(diphenylphosphino)propane or1,3-bis[di(2-methoxyphenyl)phosphino]propane.

Polymerization is conducted in the liquid phase by contacting the carbonmonoxide and the hydrocarbon reactant(s) under polymerization conditionsin the presence of the catalyst composition and reaction diluent. Usefulreaction diluents include lower alkanols, especially methanol. Typicalpolymerization conditions include reaction temperatures from about 20°C. to about 150° C., preferably from about 50° C. to about 135° C.Suitable reaction pressures are from about 1 atmosphere to about 200atmospheres, but pressures from about 10 atmospheres to about 100atmospheres are preferred. Subsequent to reaction the polymerization isterminated as by cooling the reaction and contents and by releasing thepressure. The polymer product is customarily obtained as a materialsubstantially insoluble in the reaction diluent and is recovered by wellknown methods such as filtration and decantation. The polymer is used asrecovered or is purified as by contact with a solvent or extractingagent which is selective for catalyst residues.

The polyketone polymer is stabilized according to the invention by theincorporation therein of a stabilizing quantity of an oxygen-containing,stable organic free radical derived from a phenolic compound wherein thehydroxyl group is hindered by the presence of at least one branchedalkyl substituent, and preferably two such substituents, located oncarbon atom(s) ortho to the carbon atom on which the phenolic hydroxylgroup is located. It is generally recognized that organic free radicalsare very reactive and are not capable of sustained independentexistence. However, the oxygen-containing free radicals employed as thestabilizers of the invention are capable of such independent existencethrough a combination of steric hindrance and extensive delocalizationof the unpaired electron of the free radical throughout the structure ofthe free radical. The delocalization also results in additionaldifficultly in depicting the oxygen-containing stable free radical,since the free radical exists in a number of resonance forms. Forconvenience, the free radical will be depicted with the unpairedelectron located on an oxygen atom attached to the aromatic ringadditionally containing the ortho branched alkyl substituent(s). Thisring will also contain, in the para position relative to the oxygen, agroup capable of resonance interaction with the aromatic ring to whichit is attached. The preferred oxygen-containing organic stable freeradicals have up to 30 carbon atoms and are represented by the formula##STR1##

wherein A independently is branched alkyl of from 3 to 5 carbon atomsinclusive and Z is cyano, --CO₂ R, --SO₂ R, --CH═NR, ##STR2## wherein Rindependently is aromatic of from 1 to 2 aromatic rings inclusive orcycloaliphatic and R' independently, together with the carbon atom towhich it is attached, is cycloaliphatic. The nomenclature of such freeradicals is difficult, but illustrative of the stabilizers utilized inthe compositions of the invention are the following. ##STR3## Thepreferred oxygen-containing organic stable free radical is the radicalof the above formula IIId. This material, known as Galvinoxyl, iscommercially available and is marked by Aldrich. Other stable freeradicals are produced by oxidation of the corresponding phenol by knownmethods.

The quantity of the oxygen-containing, organic stable free radical to beemployed as stabilizer in the composition of the invention is notcritical so long as a stabilizing quantity of the stable free radical isemployed. Typical stabilizing quantities of free radical are from about0.01% by weight to about 10% by weight, based on total composition.Quantities of stabilizer from about 0.1% by weight to about 5% by weightbased on total composition are preferred. The stable free radical isadded to the polyketone polymer by methods conventional for forming anintimate mixture of the polymer and the stabilizer components. Suchmethods include the dry blending of the polymer and the stabilizer infinely divided form followed by extrusion of the mixture. Alternatively,the stabilized composition is formed by blending the components in amixing device operating at high shear. The stabilized composition mayinclude other components such as antioxidants, colorants, plasticizers,fibers and other reinforcements and dyes which are incorporated byconventional methods prior to, together with, or subsequent toincorporation of the stabilizer.

The stabilized compositions are useful in the manufacture of fibers,sheets, films, laminates, containers and wire and cable of establishedutility which are produced by conventional methods such as extrusion,injection molding, thermoforming and melt-spinning. The polyketonesdemonstrate improved processability which allows processing, extrusionfor example, at a faster rate than the unstabilized polymer whenextruded through an extruder operating at constant force. The thermalstability provided to the compositions is of particular advantage when afinished article is to be used in applications where it is likely toencounter elevated temperatures, e.g., containers for food or drink.

The invention is further illustrated by the following IllustrativeEmbodiments which are not to be construed as limiting the invention.

Illustrative Embodiment I

A linear alternating terpolymer of carbon monoxide, ethylene andpropylene was produce in the presence of a catalyst composition formedfrom palladium acetate, the anion of trifluoroacetic acid and1,3-bis[di(2-methoxyphenyl)phosphino]propane. The terpolymer had amelting point of 218° C. and a limiting viscosity number (LVN), measuredin m-cresol at 60° C., of 1.84 dl/g.

Illustrative Embodiment II

Samples of the terpolymer of Illustrative Embodiment I and mixtures ofthe terpolymer and minor amounts of Galvinoxyl were passed through a 15mm Baker-Perkins extruder operating at a temperature of 240° C. Therelative feed rates of the terpolymer and the mixtures are shown inTable I.

                  TABLE I                                                         ______________________________________                                        Sample        % wt. Galvinoxyl                                                                           Feed Rate                                          ______________________________________                                        Terpolymer    0            50                                                 Mixture       0.1          74                                                 Mixture       0.5          88                                                 ______________________________________                                    

Illustrative Embodiment III

Sample plaques containing the terpolymer of Illustrative Embodiment Iwere prepared. The polymer contained 0.5% by weight of A0 330®, acommercial antioxidant, as a background stabilizer. To prepare thestabilized composition of the invention, the terpolymer was cyrogroundand dry blended with 0.1% by weight and 0.5% by weight, each based ontotal composition, of Galvinoxyl. Each mixture was tumbled overnight andextruded on a 15 mm Baker-Perkins twin screw extruder operating at atemperature of 240° C. The extruded compositions were used to makeplaques of 00.03 inch thickness by a compression molding process.

These plaques were tested for long term heat stability by placing theplaques, together with terpolymer plaques not containing stable freeradical, produced by a similar process, in a circulated air ovenoperating at a temperature of 125° C. Periodically, sample plaques werewithdrawn and bent to a 180-degree angle. When the sample becamesufficiently brittle to crack under this test procedure it wasconsidered to have failed and the time to embrittlement was recorded.The results of the testing are shown in Table II.

                  TABLE II                                                        ______________________________________                                        Sample      % wt. Galvinoxyl                                                                           Hours to Failure                                     ______________________________________                                        Terpolymer  0            156                                                  Mixture     0.1          208                                                  Mixture     0.5          208                                                  ______________________________________                                    

What is claimed is:
 1. A stabilized composition comprising:a linearalternating polymer of carbon monoxide and at least one ethylenicallyunsaturated hydrocarbon, wherein the linear alternating polymer isrepresented by the repeating formula

    --CO--CH.sub.2 --CH.sub.2)].sub.x [CO--G)].sub.y

wherein G is a moiety of an ethylenically unsaturated hydrocarbon of atleast 3 carbon atoms polymerized through the ethylenic unsaturation andthe ratio of y:x is no more than about 0:5; and a quantity of anoxygen-containing organic stable free radical effective to stabilize thepolymer against exposure to elevated temperature.
 2. The composition ofclaim 1 wherein the free radical has an unpaired electron on an oxygenattached to an aromatic ring, which ring is substituted in at least oneortho ring position with a branched alkyl group of from 3 to 5 carbonatoms inclusive and in the para position with a group capable ofresonance interaction with the aromatic ring to which it is attached. 3.The composition of claim 2 wherein the stabilizing quantity is fromabout 0.01% by weight to about 10% by weight, based on totalcomposition.
 4. The composition of claim 3 wherein the free radical isrepresented by the formula ##STR4## wherein A independently is branchedalkyl of from 3 to 5 carbon atoms inclusive, and Z is cyano, --CO₂ R,--SO₂ R, --CH═NR, ##STR5## wherein R independently is aromatic of from 1to 2 aromatic rings inclusive or cycloaliphatic, and R' together withthe carbon atom to which it is attached is cycloaliphatic.
 5. Thecomposition of claim 4 wherein y is zero.
 6. The composition of claim 5wherein the free radical is Galvinoxyl.
 7. The composition of claim 4wherein G is a moiety of propylene and the ratio of y:x is from about0.01 to about 0.1.
 8. The composition of claim 7 wherein the freeradical is Galvinoxyl.
 9. A process of stabilizing a linear alternatingpolymer of carbon monoxide and at least one ethylenically unsaturatedhydrocarbon which comprises incorporating therein a thermallystabilizing quantity of an oxygen-containing organic stable freeradical, wherein the linear alternating polymer is represented by therepeating formula

    --CO--CH.sub.2 --CH.sub.2)].sub.x [CO--G)].sub.y

wherein G is a moiety of an ethylenically unsaturated hydrocarbon of atleast 3 carbon atoms polymerized through the ethylenic unsaturation andthe ratio of y:x is no more than about 0.5.
 10. The process of claim 9wherein the free radical has an unpaired electron on an oxygen attachedto an aromatic ring, which ring is substituted in at least one orthoring position with a branched alkyl group of from 3 to 5 carbon atomsinclusive and in the para position with a group capable of resonanceinteraction with the aromatic ring to which it is attached.
 11. Theprocess of claim 10 wherein the stabilizing quantity is from about 0.01%by weight to about 10% by weight, based on total stabilized composition.12. The process of claim 11 wherein the free radical is represented bythe formula ##STR6## wherein A independently is branched alkyl of from 3to 5 carbon atoms inclusive, and Z is cyano, --CO₂ R, --SO₂ R, --CH═NR,##STR7## wherein R independently is aromatic of from 1 to 2 ringsinclusive or cycloaliphatic and R' together with the carbon atom towhich it is attached is cycloaliphatic.
 13. The process of claim 12wherein y is zero.
 14. The process of claim 13 wherein the free radicalis Galvinoxyl.
 15. The process of claim 12 wherein G is a moiety ofpropylene and the ratio of y:x is from about 0.01 to about 0.1.
 16. Theprocess of claim 15 wherein the free radical is Galvinoxyl.